6. What are the transmission routes of COVID-19?

At present, the main sources of infection are patients carrying SARS-CoV-2. Asymptomatic virus carriers can also be a source of infection. Respiratory droplet and physical contact are the main routes of transmission. The former, such as the droplets coming with sneezing, coughing and speaking, may cause infection through inhalation. The latter, such as touching the mucosa of mouth, nose, eyes and other organs with a hand that has been previously exposed to the virus, may cause infection. In a relatively closed environment, long-time exposure to high concentrations of aerosol (colloid dispersion system in which the droplets of infected persons are dispersed and suspended in the air) may also cause infection. Because we have isolated the SARS-CoV-2 from the feces and urine of patients, the aerosol or contact transmission caused by feces and urine should be noted.